1. Field of the Invention
The present invention relates generally to wheel assemblies for material handling equipment, such as carts, and more particularly to a wheel and hub assembly having a low maintenance ball bearing assembly in a hub of a wheel.
2. Description of the Prior Art
Wheels used on devices for material handling have requirements that are increasingly difficult to meet. For example, wheels used on shopping carts are expected to carry larger and larger loads as the large super stores proliferate. It is not uncommon for a shopping cart to be loaded with many cases of paper or canned goods, which can put a load of several hundred pounds on the wheels. Shopping cart wheels of a generation ago would not be capable of withstanding such loads.
In bakeries, wheels may be used on racks that are rolled into an oven while food is baked on the rack. Such wheels used in baking must withstand high temperatures, without melting or loosing lubrication.
In addition to withstanding vertical loads, cart wheels must withstand greater lateral loads, which may be placed on the wheel as a cart is pushed around a corner or along a surface that is not level.
Shopping cart wheels should also be designed for economical fabrication, since they are used in very large quantities. Furthermore, the wheel design should be able to withstand typical cleaning methods, such as a high pressure spray of washing detergent, because such cleaning can remove lubricants from wheel bearings, which may lead to noisy or poorly turning wheels.
Therefore, there is a need for an improved cart wheel that supports heavy loads; bears high lateral loads; requires little or no maintenance; protects a bearing from dirt, water, or other corrosive elements; and that rotates smoothly without wobbling.